Locking valve for hydraulic motors



Patented Aug. 11, 1953 UNITED STATES PATENT OFFICE LOOKING VALVE FOR HYDRAULIC MOTORS Application May 19, 1952, Serial No. 288,738

(Cl. 13'7l02) 3 Claims.

This invention relates to locking valves such as are frequently interposed between a selector valve and a hydraulic motor controlled thereby, for locking the motor against movement when the selector valve is in neutral position.

Such valves as previously constructed prevent escape of fluid from the motor but do not prevent entry of fluid to the motor. Under some conditions, high shock forces applied to the motor by its load cause it to compress the fluid in one line and thereby move sufficiently to draw in fiuid through the other line, which fluid is then trapped by the locking valve. As a result, excessive pressures may be built up in the lines between the motor and the locking valves.

An object of the present invention is to provide a locking valve that prevents flow to a circuit controlled thereby as well as away therefrom.

Another object is to provide a valve having two line ports respectively associated with two load ports, in which pressure in either line port in excess of the pressure in its associated load port communicates each supply port with its associated load port, but in which pressure in either load port exceeding the pressure in the supply ports breaks communication between the load ports and the supply ports.

Other more specific objects and features of the invention will become apparentfrom the description to follow.

In the drawing:

Fig. 1 is an end elevation view of a valve incorporating the invention;

Fig. 2 is a longitudinal vertical section taken in the plane IIII of Fig. 1;

Fig. 3 is a longitudinal section taken in the plane IIl-III of Fig. 1;

Fig. 4. is a longitudinal section taken in the plane IV-IV of Fig. l; and

Fig. 5 is a schematic diagram showing a system incorporating the valve of the present invention.

Referring first to Figs. 1, 2, 3, and 4, the valve therein depicted comprises a body it having a pair of line ports H and Na and a pair of load ports [2 and 12a respectively. In operation, as will appear later, one of the load ports [2 may be connected to one end of a hydraulic motor cylinder and the other ports 12a may be connected to the other end of the motor cylinder. One of the line ports H may be connected to a pressure line and the other line port I la connected to exhaust or vice versa.

The body It is provided with a central cylindrical bore l3 containing a reciprocable piston M andclosed at its opposite ends by plug assemblies 2 l5 and IEct respectively. Since the structures at opposite ends of the valves are identical, only that at the left end will be described. Corresponding elements at the other end of the valve bear the same reference numeral with the SllfilX a.

The plug assembly [5 comprises a plug body 16 having threads thereon for screwing into associated threads H in the body It) and having a reduced inner end portion which fits in the cylindrical bore [3 and seals therewith at longitudinal spaced points by means of the sealing rings is and I9 respectively. The plug body 16 has a cylindrical passage 29 extending thereinto from the right end, and has a smaller cylindrical passage 2! extending beyond the passage 28. The outer end of the passage 28 contains a valve seat 22 against which a ball poppet 23 is adapted to seat. The poppet 23 is normally urged against the seat 22 by a plunger 24 which is slidable in the cylinder 2! and is urged toward the poppet 23 by a spring 25 which is compressed between the plunger 2! and an adjusting screw 2% which is threaded into the outer end of the plug body it.

The cylinder 28 is communicated by lateral apertures 27 with an annular groove 28 in the outer surface of the inner end portion of the plug body i6, which groove is in communication with the port l2 in the valve body Hi. The left or outer end of the cylinder 2! is communicated by passages 3! in the plug body IS with an annular space 32 defined between the plug body 56 and the valve body in, which annular space 32 communicates with one end of a passage 33 in the body it (Fig. 3) the other end of which passage communicates with the annular groove 28a at the other end of the valve. Similarly, the annular space 32c at the right end of the valve is communicated through a passage as in the body It with the annular groove 28 at the left end of the valve.

The piston M has stems 35 and 35a projecting from opposite ends thereof, which stems are normally spaced from the poppets 23 and 23a but which engage one or the other of the poppets when the piston is moved in one direction or the other out of its mid position in the cylinder l3.

Referring now to Fig. 5 the valve may be connected between a hydraulic motor 29, shown as a cylinder containing a piston ll, and a selector valve 2 which supplies pressure fluid to one of the ports M, Ma, and connects the other to exhaust. The valve 42 is shown as having line ports 53 and it connected to the line ports H and Ha.

respectively, having a pressure port 45 connected to the output of a pump 46, and having an eX- haust port 47 connected to a reservoir 48 which also supplies the pump 46. The valve IG functions in the system shown in Fig. as follows:

When the selector valve 42 is in neutral position, as shown, the pump port 45 is cut off and both of the line ports 43 and 44 are connected to the exhaust port 41 so that no pressure exists in the line ports II and Ila of the valve I2. If the selector valve 42 is rotated out of neutral position in one direction it applies pressure fluid from the pump 46 to the line port I I while leaving the other line port Ila, connected to exhaust. If the selector valve is rotated in the opposite direction out of neutral position, the pressure is applied to the line port Ila. and the line port II is left connected to exhaust. It will be noted that with the valving arrangement shown, both of the line ports II and Ila are always connected to exhaust when the valve 42 is in neutral position, and one of these two ports is always connected to exhaust even though pressure fluid is applied to the other.

If it is desired to move the motor piston 4| to the right, the selector valve 42 is manipulated to apply pressure fluid to the line port II. This fluid flows into the cylinder I3 on the left side of the piston I4 and past the check valve 23 and thence out through load port I2 to the left end of the motor 40. The pressure of this fluid in the left end of the cylinder I3 not only opens the check valve 23 directly but moves the piston I4 to the right, so that the stem a thereof engages the check valve 23a and opens it, thereby permitting return of fluid from the right end of the motor through the load port I2a and past the check valve 23a to the line port Na and thence through the valve 42 back to the reservoir 4B. plied to the line port IIa the check valve 23a is directly opened by the fluid and the piston I4 is moved to the left so that its stem 35 opens the other check valve 23 to permit return of fluid from the left end of the motor 40.

It will be noted that pressure fluid in the line port II will also be applied past the check valve 23 and through the passage 34 to the right or outer end of the cylinder 2 la. thereby urging the plunger 24a to the left.

tion to the opening force applied to the poppet 23a by the piston I4. However the piston I4 will always prevail over the plunger 24a because of its substantially larger area.

When the selector valve 42 is restored to neutral position, after an operation as described above, the pressure in the line ports II and IIa is reduced to a very low value, but pressure remains in the opposite ends of the motor 40 because they are then cut off from the line ports II and Na, by the closing of the check valves 23 and 230.. It will be observed that if the pressure tends to increase in either of the load ports I2 or I 2a it will force the check valve 23 or 23a. even more tightly against its seat, so that there is no tendency for leakage of fluid from the motor 40 back through the valve It to the line ports II and Ila.

However, with valves of this type, as previously constructed, if powerful reaction forces are applied to the motor piston 4|, suction forces can be developed in one or the other of the load ports I2 or 12a. which would draw in additional fluid past one of the check poppets 23 or 23a.

Obviously if the pressure fluid is ap- The force exerted on J the poppet 230. by the plunger 24a is in opposi- Thus let it be assumed that a powerful force is applied to the motor piston 4| urging it to the right. This tends to force fluid out of the right end of the motor 40 and through the load port I20; and past the check valve 23a. As previously noted, such flow cannot occur, but there may be some compression of the fluid in the ducts and passages or some expansion of the ducts which would permit the piston 4| to move a short distance in response to the force. This movement would reduce the pressure in the left end of the motor 40 and in the load port I2 tending to draw in additional fluid past the poppet 23. As a result of this action it has been found in practice that with locking valves as previously known, powerful alternating forces applied to the motor piston 4| would pump fluid into one or both ends of the motor 40 developing high and dangerous pressures in the motor and the lines between the motor and the valve l0.

Such pumping and generation of high pressures is prevented by the present invention because a high pressure, for instance in the load port I2a, is applied through the passage 33 and the passages 32 and 3| to the left end of the plunger 24, thereby urging that plunger powerfully to the right and hold the poppet 23 against its seat despite the existence of a low pressure in the load port I2.

Similarly the poppet 23a is prevented from opening in response to low pressure in the load port I2a, because simultaneously the high pressure existing in the port I2 is applied through the passage 34 to the right end of the plunger 24a which holds the poppet 23a tightly against its seat.

It will be observed therefore that the locking valve of the present invention is locking in the full sense of the word, since when pressure is absent from the line ports II and Hit, the pressure in either of the load ports I2 or |2a locks both of the poppets 23 and 23a tightly against their seats, preventing any flow of fluid either in or out of the load ports I2 or I2a.

Although for the purpose of explaining the invention, a particular embodiment thereof has been shown and described, obvious modifications will occur to a person skilled in the art, and We do not desire to be limited to the exact details shown and described.

We claim:

1. A valve of the type described comprising: a body having two line ports and two load ports; means defining two flow paths one between one line port and one load port and the other between the other line port and the other load port; a check valve in each flow path directed to prevent flow from each load port to its associated line port; first motor means responsive to pressure in either line port to open the check Valve associated with the other line port; and second motor means differentially responsive to the pressures in said two load ports for urging into closed position the check valve associated with the load port of lower pressure.

2. A valve in accordance with claim 1 in which said second motor means comprises two motors respectively associated with and adjacent to said two check valves; means connecting each motor between said two load ports each motor being movable against its associated check valve to urge it into closed position in response to pressure in the load port associated with the other check valve.

3. A valve according to claim 2 in which each of said check valves comprises a seat and a poppet and each of said two motors of said second Referelwes Clted 111 the file 0f thls patent motor means comprises a cylinder aligned with UNITED STATES PATENTS its associated poppet on the side thereof remote from the seat and a plunger in said cylinder 5 Number Name Date 2,389,654 Van Der Werf Nov. 27, 1945 movable against the poppet to urge 1t against 2 483 312 01a Sept 27 1949 the seat; the end of said cylinder adjacent said 2621676 g 1952 poppet communicating directly with the associated load port; and passage means connecting the other end of the cylinder to the other load 10 port.

CLINTON E. DEARDORFF. JOSEPH B. GUNN. 

